Define competitive gameplay playtest benchmarks

[Swarek]

Goal

Define repeatable playtest benchmarks for hitboxes, knockback, movement, recovery, shields, and combo escape.

Acceptance criteria

• Describe a small set of deterministic training scenarios and expected measurements.
• Cover low, medium, high, and sudden-death damage states.
• Include fast, average, and heavy open fighters.
• Measure at least launch distance, hitstun, recovery reach, shield response, and common combo escape windows.
• Store results in a format that can be compared between releases.
• Turn clear regressions into automated tests where feasible.

This issue is about building evidence for balance decisions, not copying another game's proprietary tables.